1. Field of the Invention
This invention relates to emergency lighting luminaires, and more particularly to self-contained unit equipment luminaires for recessed installation in a ceiling or wall.
2. Description of Prior Art
Adequate illumination of emergency egress routes from the interior of buildings is a requirement of nearly all modern building codes and standards. For instance, the National Fire Protection Association (NFPA) issues standards for emergency lighting illumination levels and uniformity ratio along the egress path.
The current NFPA Life Safety Code requires that “Emergency illumination shall be provided for a period of 1½ hours in the event of failure of normal lighting. Emergency lighting facilities shall be arranged to provide initial illumination that is no less than an average of 1 footcandle (10 lx) and a minimum at any point of 0.1 footcandle (1 lx) measured along the path of egress at floor level. Illumination levels may decline to 0.6 footcandle (6 lx) average and a minimum at any point of 0.06 footcandle (0.6 lx) at the end of the emergency lighting time duration. A maximum to minimum illumination uniformity ratio of 40 to 1 shall not be exceeded.” NFPA Life Safety Code Section 5-9.2.1 One way that designers meet such standards is through the use of “unit equipment” luminaires, which generally consist of a self-contained rechargeable battery, battery charging circuitry, lamps, and circuitry for switching to battery power and illuminating the lamps upon the occurrence of an emergency condition, such as a power failure.
Traditionally, unit equipment luminaires have a housing which contains the electronic components. The luminaires typically are hung from a wall and the lamp adjusted as desired. Thus, such a unit equipment luminaire protrude into the living space of the room or corridor where they are located.
However, exposed unit equipment luminaires are not always compatible with the interior design of space. Additionally, such exposed luminaires are subject to both accidental abuse and intentional vandalism.
Emergency lighting designers have presumably attempted to address such issues with devices such as those described in U.S. Pat. Nos. 4,802,065, and 5,851,061.
For instance, U.S. Pat. No. 4,802,065 to Minter, et al., issued Jan. 31, 1989, teaches an emergency lighting fixture for mounting in a ceiling. The fixture has a drop down panel normally enclosing an opening in the ceiling. An energized solenoid or motor hold the panel in the closed position. A lamp is mounted to the drop down panel such that upon failure of a.c. power, the weight of the panel and lamp causes the panel and lamp to drop down to illuminate a path of egress. This design, while functional, has added energy, component and maintenance costs associated with the continuously energized solenoid or motor and the moving parts associated therewith. Additionally, this design will not work in a wall installation, since it must be oriented such that the weight of the panel and lamp will cause the panel to drop down.
U.S. Pat. No. 5,851,061 to Hegarty, issued Dec. 22, 1998, also teaches a recessed emergency light fixture having a hinged panel which normally covers the installation opening. Upon failure of the normal a.c. power to the fixture, a solenoid opens the panel, which has a mirrored rear surface. Illumination from a lamp within the fixture is then reflected off of the mirrored surface to light a path of egress. This design provides for mounting in either a ceiling or wall, since the panel is opened by the solenoid rather that gravity. The design has added costs due to the additional components (solenoid and linkage) and the maintenance issues associated with those moving parts. Further, efficiency of the fixture in the event of a power failure is likely reduced by the power consumed by the solenoid in holding the panel in an open position.